The major drawback of the bow as a hunting weapon is the rainbow-like trajectory of the arrow, requiring accurate distance estimation, particularly at hunting distances. For example, at a distance of 35 yards, a range estimation error of as few as two or three yards can cause a complete miss on a deer-size target, or worse yet, a leg hit. To further complicate matters, a downhill shot, for example one from an elevated tree stand, causes the arrow to fly higher than would be the case in a horizontal shot at the same distance. The same applies to an uphill shot. Skilled bowhunters develop their range-estimation ability through dedicated practice in field conditions, some shooting "instinctively", i.e. without the use of sights or even conscious range-estimation.
Hand-held range-finding instruments are available and present one solution to the problem, but are awkward to use and require extra movement at a time when any movement is undesirable. Crude range estimation devices are available, relying on spaced stadia wires subtending a set angle, which brackets an "average" deer's chest at certain specified distances, but these are not widely used owing to wide variations in body size within and between species. Neither aid corrects for differences in elevation between the target and the archer.
More sophisticated bow-mounted aids are known in prior art. These fall into two main classes: the first comprises sights incorporating optical range-finders which measure the line-of-sight distance but not the angle of inclination or declination to the target; the second class relies on measurement of the angle of declination from an elevated shooting position but not the line-of-sight distance to the target.
Aids of this first type include U.S. Pat. No. 3,136,697 dated Dec. 29, 1964, to D. S. White, claiming an optical range-finder based on a dual spaced mirror device and coupled sighting element; U.S. Pat. No. 2,788,701, dated Apr. 16, 1957, to G. G. Browning, claiming the use of a multi-mirror device; U.S. Pat. No. 4,555,856, dated Dec. 3, 1985, to D. E. Brown, claiming a third adjusting compensating mirror and cam-coupled sight pin; U.S. Pat. No. 4,646,444, dated Mar. 3, 1987, to J. W. Carey, claiming a self-indicating planar/parabolic mirror combination; and U.S. Pat. No. 4,178,693 to G. D. Smith, claiming a two-mirror, split image bowsight incorporating a cam-controlled alignment mechanism. All of these devices are accurate only when the shot is approximately level, and where one or more sight components is customized to the specific shooter, bow, and projectile. For example, Smith's cam and Brown's programmed slide must be customized by highly sophisticated mathematical modelling techniques or by trial and error. Cary's parabolic mirror is provided with means of adjustment relying on the deflection of a flexible, variable thickness mirror. Cary's device, does not have precise horizontal aiming point providing suitable alignment with a particular spot on a nondescript target such as a deer.
The second class of aids includes U.S. Pat. No. 4,120,096 dated October 1978, to Keller, claiming a pivoted sight whose position relative to the sight picture is appropriately elevated as the bow is tilted from the horizontal; U.S. Pat. No. 4,796,364, dated Jan. 10, 1989, to J. A. Amacker, claiming a dual sight comprising a pendulum sight for shooting from an elevated position and a multi-pin sight for use on level ground, each of which can be secured out of the archer's line-of-sight when not in use; U.S. Pat. No. 4,711,036, dated Dec. 8, 1987, to E. Morris claiming two versions of a pendulum-actuated sight; U.S. Pat. No. 4,325,190, dated Apr. 20, 1982 to T. Duerst, claiming a plurality of sights selectively illuminated accordig to the angle of declination of the bow via an electronic circuit incorporating a plurality of switches; and U.S. Pat. No. 4,400,887, dated Aug. 30, 1983 to J. D. Mason, claiming a plurality of sights and a means for selectively causing one pin to be readily distinguishable from the others according to the angle of declination of the bow, via a pendulum-mounted colored lens positioned to selectively interrupt multiple fiber-optic cables. None of these devices serves as a range-finding aid on level or upwardly sloping ground, nor do they function properly where the elevation of the archer relative to the target is unknown (for example where the elevated stand is situated above sloping ground) or where the archer is significantly above or below the restricted height range for which the sight is calibrated. Furthermore, except for the precalibrated multi-pin sights of Duerst and Mason, all of these aids provide the same sight correction for all bow/shooter/projectile combinations. In practice, the vast majority of bowhunters shoot and hope for the best, resulting in a higher incidence of poor hits and lost game than would be the case if an accurate range-finding sight were used. Indeed, increasing controversy over the humaneness of the bow as a hunting weapon in the hands of the average hunter mandates the development of such a device.
The present invention is a sight which not only allows the accurate estimation of range, but also indicates which sight pin to use, taking into account deviations from the horizontal. (Bowsights typically have multiple pins, each set for a different distance.) The device measures the distance and angle to the target, indicating the appropriate pin by means of a light source within each pin. Thus, the sight is both error-proof (no room for error in pin selection) and fail-safe (i.e. the sight can be used as a conventional bowsight if the range-finding mechanism becomes inoperable). The range-finding mechanism is operated by the bow hand, allowing the hunter to draw, estimate, aim, and release in one fast, fluid movement. The lighted pin feature facilitates sighting in low light conditions. Finally, the sight is designed to attach to the standard bushings provided by all bow manufacturers, allowing easy installation without special tools.